Now that we have identified the structures making up the various walls
of the axilla, it is time to take a look at its contents. We will first
examine the blood vessels, then the nerves and finally, the lymphatics,
in that order.

Axillary Artery

The axillary artery begins at the lateral border of the first rib as
a continuation of the subclavian artery. It changes its name to brachial
artery at lower (inferior) border of the teres major muscle. For purposes
of description, it is broken up into three parts by its relation to the
pectoralis minor muscle. The first part is between the lateral border of
the first rib and the medial border of the pectoralis minor, the second
part is behind the pectoralis minor and the third part is between the lateral
border of the pectoralis minor and the inferior border of the teres major.

Axillary Vein

The axillary vein lies along the medial side of the artery and is a continuation
of the basilic vein. It begins at the inferior border of the teres major
m. and ends at the lateral border of the first rib, where it becomes the
subclavian v. It receives tributaries that parallel the branches of the
axillary artery. The cephalic v. joins the axillary v. just before it becomes
the subclavian. We won't give any further details here. This doesn't mean
that it isn't important for maintaining proper function of the upper limb.
I may be injured in sports as well as when a person uses a crutch. Penetrating
wounds in the larger upper part are serious because air might enter into
the venous system.

Vena comitans

The veins that run with their corresponding arteries are frequently
multiple
(2 or 3 interconnected veins). This interconnected venous network is
called the vena commitantes.